1. Field of the Invention
The invention is directed to a method for the operation of an internal combustion engine having a plurality of cylinders, namely, a method for cylinder-specific detection of misfires.
2. Description of the Prior Art
Internal combustion engines must meet increasingly stricter emission limit values. One possibility for meeting these emission limit values is to optimize the operation of the internal combustion engine by a control. In this regard, it is also already known in an internal combustion engine to control the individual cylinders of the internal combustion engine individually. Another option for meeting these emission limit values is guiding exhaust gas of the internal combustion engine through an exhaust gas aftertreatment system in order to reduce emissions of exhaust gas components such as soot, CO, NOx or hydrocarbons.
Exhaust gas aftertreatment systems known from practice have a high oxidation capacity for hydrocarbons. Because the oxidation of hydrocarbons takes place exothermally, excessive concentrations of hydrocarbons in the exhaust gas can cause thermal damage to the exhaust gas aftertreatment system.
High concentrations of hydrocarbons in the exhaust gas that lead to thermal damage to an exhaust gas aftertreatment system may be caused, for example, by misfiring of cylinders in the internal combustion engine because, during misfires of this type, the fuel introduced into these cylinders reaches the exhaust gas aftertreatment system without being combusted. In this case, there is a particularly high risk of damage to the exhaust gas aftertreatment system.
Misfires of this type are especially critical in gas engines that have oxidation catalytic converters, e.g., CH4 oxidation catalytic converters or CH2O oxidation catalytic converters, in the region of the exhaust gas aftertreatment system. Oxidation catalytic converters of this kind are exposed to a particularly high risk of damage from misfires in cylinders of a gas engine.
Therefore, it is important to detect misfires in cylinders in an internal combustion engine.
A device by which misfires in an internal combustion engine can be detected is known from DE 25 28 785 A1. Temperature sensors are used for this purpose. However, temperature sensors are not capable of safely detecting sporadically occurring misfires because the thermal inertia of temperature sensors is too high. On the contrary, temperature sensors can only be used to detect a persistently malfunctioning cylinder. However, it is precisely during sporadic misfires of cylinders in an internal combustion engine that large temperature increases can occur in the region of an exhaust gas aftertreatment system in catalytic converters of the exhaust gas aftertreatment system, which leads to damage of these catalytic converters. Therefore, it is important that sporadic misfires can also be safely and reliably detected.